It is sometimes desirable to inject a substance into a subject with more precision than a typical syringe. In view of the presence of different layers, for example in a human being, it may be necessary to deliver a substance very precisely within just one distinct tissue layer. Different layers are distinguishable such as skin, mucosa, subcutis, fascia, muscle, nerves, or joints. For example, human skin comprises several different layers. The epidermis is the outer skin layer with a thickness of about 30 to 2000 μm. The dermis is located beneath the epidermis with a thickness of about 500 to 1500 μm. The subcutis is located beneath the dermis with a thickness of about 500 to 30,000 μm. In certain applications, it is desirable to specifically deliver substances such as cells to specific locations within the skin.
It is necessary to provide means that allow that substances such as cells are injected in the desired physiological tissue. As one particular example, in the field of biological hair research there is a need for the accurate application of so called “dermal sheath cup” cells (“DSC”) which have potential for hair follicle regenerating. Similar demands exist concerning further injection applications. For example the injection within the skin during cosmetic or aesthetic treatment requires further distinct means for the injection.
A further application concerns the injection into muscle tissue, joints, fascia, fat tissue, cartilage, submucosal tissues, or tendons. Such applications are often necessary after injuries which occur during sports or exercises. There is a constant need to treat tissue and distinct layers from the outside in a simple and reliable way.
The application of substances (e.g., liquids, biologics, or cell suspensions) within the dermis, epidermis or subcutis as well as muscle tissue layers or tendons requires a skilful handling by a medical doctor. In addition, the application of such substances can involve distinct requirements. For example, with respect to cells there is a need to deliver them as near to the respective tissue layer which resembles the physiological tissue layer of these cells in situ as possible. Secondly, there is also a need to apply the cells in a very careful way. In particular cells, such as stem cells or freshly prepared primary cells, are sensitive in view of pressure which arises during the application. Such pressure occurs for example when cells are applied via a narrow cannula which results in a high compression of the cells. Such a compression and the resulting shear stress which acts on the cells are harmful. The consequence of this can be that cells are severely damaged and probably even loose their viability.
It is possible to apply cells to the scalp of a subject with a standard syringe having a needle of a distinct size and length. This has however the disadvantage that it is not possible to apply the cells in a constant manner since the needle is shifted each time the injection site is changed. Accordingly, the angle between the injection needle and the scalp surface is not constant and will be very likely altered during each injection. Further, the injection depth will very likely vary during the different injections, since there is no measure of how deep the injection has to be performed if it is conducted with a standard syringe having an injection needle which is only guided by hand.
WO 02/083216 A1 describes a device and a method for the intradermal injection of substances. The afore-mentioned device allows the injections in a defined depth of penetration which allow an intradermal delivery, wherein the needle is injected perpendicular to the plane of the skin.
WO 94/23777 A1 describes an intradermal injection device which allows also a subcutaneous injection and foresees the application of a vacuum.
However, none of the devices of the prior art allows the delivery of liquid substances, such as cells, without the application of pressure or shear-stress. Furthermore, none of the devices of the prior art allows the application of liquid substances, such as cells, in a reliable way which ensures that the application occurs in the optimal physiologic site.
The application of cells to, for example, the scalp of a subject, requires distinct requirements as outlined above. Further, it is necessary that the cells are applied within a single layer or region and in a distributed manner. Accordingly, it is desired that the cells are not injected in punctual form but preferably in a more dispersed way.
Therefore, there is a need to provide a device which overcomes the problems as described above and which allows the delivery of substances, in particular biological substances, such as cells, in a careful manner and at the desired physiological site in a reliable and reproducible way. This underlying technical problem is solved with the injection device as defined within the claims.
The injection device according to the present invention provides distinct advantages over the prior art since liquid substances and cell suspensions can be applied in a careful and gentle way and the delivery is conducted in the desired physiologic tissue layer.
For the purpose of illustration of the present invention, the present invention is shown in illustrative form, it being understood however, that the invention is not limited to the precise form shown in the figures or examples.